Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/02—Refining fats or fatty oils by chemical reaction
  • C11B3/06—Refining fats or fatty oils by chemical reaction with bases

Definitions

• the present invention relates to a method for removing free fatty acids from fats and oils of biological origin or their damper condensates by extraction.
• Oils and fats of biological origin play an important role in human nutrition and as raw materials for the chemical industry. For example, they serve as raw materials for the production of surfactants, plasticizers, waxes, lubricants, fatty alcohols, etc.
• the essential components of fats and oils are the triesters of glycerides and fatty acids, the so-called triglycerides.
• Fats and oils are determined a) by the chain length of the fatty acids, b) by the degree of saturation of the fatty acids and c) by the distribution of the various fatty acids over the three hydroxyl groups of the glycerol. Fats with a high proportion of saturated fatty acids are generally solid at ambient temperature. Fats or oils from predominantly unsaturated fatty acids are liquid at ambient temperature.
• the fats and oils of biological origin contain a number of by-products that affect shelf life, smell, taste and appearance.
• the most important by-products are: suspended matter, organic phosphorus compounds, free fatty acids, coloring and odorants.
• Mucilage and other complex colloidal compounds can promote the hydrolytic breakdown of the fats and oils during their storage and are disruptive in the further refining. That is why they are removed by the process of so-called degumming.
• the degumming is based on hydration with water or direct steam.
• the organic phosphorus compounds (phosphatides) absorb water, swell and become insoluble. After phosphorus compounds and suspended matter have been removed by degumming and, if appropriate, filtration, the further task is to separate free fatty acids and colorants and odorants.
• the fatty acid content of the refined fats and oils should generally be less than 0.1% by weight. While longer-chain free fatty acids usually do not affect the taste, the short-chain fatty acids have a soapy, rancid taste.
• the deacidification to remove the free fatty acids is mainly carried out by treatment with aqueous alkali solutions or by steaming at temperatures of about 220 ° C. The removal of the free fatty acids by esterification with glycerol or with a monohydric alcohol, by selective solvent extraction or by adsorbents is of less importance. The previously known deacidification processes are explained in more detail below.
• alkaline solutions Treatment with alkaline solutions as the most widely used method can be carried out batchwise or continuously.
• Weakly alkaline solutions are generally sprayed onto the oil at 90 ° C and percolate downward through the heated oil. Stronger alkalis (4n to 7n), on the other hand, are usually stirred into the oil at 40 to 80 ° C.
• the oil or fat After deacidification and removal of the soap stick, the oil or fat is washed with heavily diluted lye (approx. 0.5 n) and then with water to remove soap residues down to at least 0.05% by weight.
• So-called steam deacidification has been developed as an alternative.
• this process also known as physical refining or distillative deacidification
• the free fatty acids are also continuously removed from the crude oils with hot steam under vacuum. It is not so important that the fatty acids are distilled off completely, because fatty acids remaining in small amounts can expediently be removed by post-refining with lye.
• the crude fat Before deacidification by distillation, however, the crude fat must be freed as completely as possible of mucilage, phosphatides and traces of metal - usually by treatment with phosphoric acid - since the accompanying substances can lead to dark, unpleasant tasting substances during distillation, which can then hardly be removed.
• Steam deacidification takes place at relatively high temperatures, for example palm oil is deacidified with direct steam at 220 ° C. The high temperature destroys a whole range of oil (or
• Fat contained and desirable substances per se, for example antioxidants that increase the shelf life of the oil, or drives these substances into the so-called steam condensate, which is obtained after the condensation of the hot steam used for deacidification.
• the neutralization of oils and fats by separating the free fatty acids from the crude fat by means of selectively acting solvents is another method that is particularly suitable for highly acidic oils and fats.
• liquid extraction with ethanol enables the deacidification of olive oil with 22% by weight of free fatty acids down to about 3% by weight of free fatty acids.
• Another extractant that only dissolves free fatty acids and very highly unsaturated triglycerides at suitable temperatures is furfural.
• the Selexol process liquid propane is used as an extractant in countercurrent. The liquid Propane selectively dissolves saturated neutral oil, while fatty acids, oxidation products, unsaponifiable matter and the highly unsaturated glycerides are hardly dissolved and remain. This process is mainly used for the fractionation of fish oils and fish liver oils.
• a decolorization step is generally switched on. It is usually decolorized with solid adsorbents, e.g. Bleaching earth and activated carbon. Air or chemical bleaching plays a minor role in edible fats.
• odors and flavors are removed from the deacidified and bleached oils and fats.
• Deodorization is essentially a steam distillation, in which the volatile compounds are separated from the non-volatile glycerides.
• the aromas and flavors are predominantly aldehydes and ketones, which have formed through autoxidative or hydrolytic reactions during the processing and storage of fats and oils.
• the low partial pressure of the connections to be removed requires that the damping be carried out in a vacuum. Steaming is usually carried out at 180 to 220 ° C and a pressure of 6 to 22 mbar. For reasons of environmental protection, the waste water from the alkaline deacidification must be carefully processed, which is associated with costs.
• alkanolamine preferably ethanolamine
• alkaline extraction agent which dissolves the free fatty acids as soaps in the aqueous phase. Residues of alkanolamines dissolved in the raffinate are washed out by washing with dilute sulfuric acid, acetic acid, lactic acid, citric acid or hydrochloric acid solutions.
• the invention is therefore based on the object of specifying an improved process for the deacidification of oils and fats of biological origin which, on the one hand, can also handle high levels of free fatty acids without technical problems, and on the other hand enables the production of very high-quality fats and oils, such as those be desired by the food industry, for example.
• the process according to the invention is based on the fact that, surprisingly, when deacidifying oils (or fats) with a high proportion of free fatty acids by means of aqueous solutions of organic bases, for example 2-dimethylaminoethanol, no viscous soapstock forms if the amine content in the aqueous Solution is at least about 20 wt .-% and at most about 60 wt .-% and preferably between about 30 wt .-% and about 40 wt .-%. Instead, both the oil phase and the extract phase are low viscosity liquids under such conditions. The phase separation runs quickly within a few minutes; the resulting phases are clear.
• the concentration of the organic base, for example 2-dimethylaminoethanol, in the aqueous solution must be at least about 20% by weight, better still about 30 to 40% by weight, so that no viscous soap stick or cloudy
• the aqueous solution used for deacidification must have a content of about 20% by weight to about 60% by weight of organic nitrogen compound.
• Residues of the basic nitrogen compounds dissolved in the raffinate are preferably washed out with water or with dilute acetic acid, lactic acid, citric acid, sulfuric acid or hydrochloric acid solutions.
• traces of the basic extractant in the raffinate are removed by stripping with carbon dioxide.
• the carbon dioxide can be used as a dilute gas or as a dense, supercritical gas to remove traces of the basic nitrogen compounds used from the raffinate.
• the extraction agent used according to the invention for example an aqueous solution of 2-dimethylaminoethanol
• the vapor pressure of the water is approximately equal to or higher than the vapor pressure of the basic nitrogen compound (s) used.
• the water and the basic organic compound are distilled off together, or the water is first preferably distilled off, the ratio of basic compound to water remaining constant or increasing and the formation of a viscous soap stick being avoided. If the vapor pressure of the basic compound were higher than the water vapor pressure, the ratio of the basic compound to water would decrease and finally the formation of a viscous soap stick would occur.
• the boiling temperature of the basic nitrogen compound (s) must be on the one hand equal to or higher than the boiling temperature of the water and on the other hand lower than the boiling temperature of the fatty acids to be extracted.
• Suitable basic, organic compounds for the process according to this invention should have the following properties: a) the compound should, if possible, not form any amides with the free fatty acids; b) the compound should be miscible with water in any ratio; c) the boiling temperature of the compound should be equal to or higher than that of water, d) the odor nuisance caused by the aqueous solutions should be as low as possible.
• suitable organic nitrogen compounds are: N-methylmorpholine, 2-dimethylaminoethanol, 3- (diethylamino) -1-propanol, 2-diethylaminoethanol, 1- (dimethylamino) -2-propanol, dimethylformamide,
• tertiary amines are preferred because of their higher basicity of binary and monosubstituted amines.
• starting materials that can be deacidified well using the process according to the invention are beef tallow, lard, fish oil, corn oil, slaughter fat, palm oil, soybean oil, rapeseed oil, sunflower oil, rice germ oil, cottonseed oil, olive oil, peanut oil, safflower oil, coconut oil, pal kernel oil, grape germ oil, Wheat germ oil, etc.
• the oils and fats to be deacidified should be degummed and filtered, especially if more than 100 pp of phosphatides are present.
• the fat or oil prepared in this way still contains dissolved oxygen, which should also be removed before further processing.
• the process according to the invention then deacidifies the starting material while protecting temperature-sensitive compounds such as carotenes, tocotrienols, tocopherols, etc. These compounds, which are also important in terms of nutritional physiology, become one in conventional physical refining, which is carried out by means of direct steam, due to the high temperatures Most of them destroyed or driven out.
• the method according to the invention is also outstandingly suitable for removing the free fatty acids from the damper condensates of fats and oils, which can be obtained by means of the conventional physical refining just mentioned, i.e. by means of steam deacidification.
• damper condensates generally contain free fatty acids in very high concentrations, mostly in the range from about 80 to 94% by weight. Due to the high content of free fatty acids, the extracting agent used according to the invention, ie the mixture of organic base and water, must be richer in the basic nitrogen compound than previously described in connection with the deacidification of fats and oils. The proportion of organic nitrogen compound in the extractant should be at least about 40% by weight. If such an aqueous solution rich in basic nitrogen compound, for example 60% by weight of 2-dimethylaminoethanol and 40% by weight of water, is used as the extractant for the liquid damper condensate added, you get a liquid, homogeneous mixture.
• One to four parts, preferably two to four parts, of an alkane and / or an ester, in particular an ethyl acetate, are then added to one part of the liquid mixture to this liquid mixture.
• the fats and oils present in the damper condensate are essentially dissolved in the alkane and / or ester phase.
• the by-products such as tocopherols, tocotrienols and phytosterols, which are also dissolved in the steam condensate, also pass into the alkane phase with high selectivity.
• the water-containing phase with the free fatty acids contained therein is of low viscosity, so that a phase separation took place approximately within 20 minutes after interruption of the mixing.
• the raffinate (alkane phase or ester phase) which results after the aqueous phase has been separated off is, depending on the starting product, highly enriched in by-products, such as tocopherols, phytosterols, tocotrienols. Such valuable by-products can be obtained from such concentrates under economically attractive conditions.
• alkanes examples include propane, butane, hexane, petroleum ether, heptane, heptane fractions, octane, etc.
• propane propane
• butane or propane as a solvent for the formation of two phases
• the pressure in the mixing vessel must at least correspond to the respective vapor pressure so that the butane or propane is in liquid form.
• esters are the ethyl acetate, for example ethyl acetate, propyl acetate, butyl acetate or a mixture thereof.
• the concentration of free fatty acids in the starting material to be treated is more than about 50% by weight
• the addition of alkanes is required so that the overall system (starting material and extractant) remains two-phase.
• the addition of alkane or ester accordingly ensures the formation of two easy-to-handle liquid phases even at high concentrations of free fatty acids in the starting mixture, and extracts with high concentrations of free fatty acids can be obtained with the extractant used according to the invention by countercurrent extraction.
• the solvent ratio can be small, which has an advantageous effect on the economy of the method according to the invention.
• a starting product (oil, fat or steam condensate) is fed to a first extraction column 12 through a line 10.
• the free fatty acids are extracted with high selectivity from the starting product using an extracting agent which consists of a mixture of a basic nitrogen compound and water.
• the extractant used contains at least about 20% by weight and at most about 80% by weight of the organic nitrogen compound (organic base). Concentrations of the basic nitrogen compound of about 30 to 40% by weight have proven to be particularly favorable. However, the concentration of basic nitrogen compound can easily be selected to be even higher.
• the oil or fat freed from the free fatty acids is fed through a line 14 to a washing column 16 (extraction column), in which residues of the basic nitrogen compound are washed out with water or with an aqueous solution which contains an acid, and leaves the washing column 16 as Raffinate R.
• the washing solution emerging at the top of the washing column 16 through a line 18 is then worked up by distillation in a distillation column 20. In doing so
• the extraction agent containing the free fatty acids, drawn off at the top of the extraction colon 12, is fed through a line 26 to a second distillation column 28.
• Water and the basic nitrogen compound are obtained as the top product during distillation in the distillation column 28, while the extract containing the extracted free fatty acids and some neutral oil is withdrawn as a bottom product through a line 30 from the distillation column 28.
• Distillation column 28 is fed as extraction medium through a line 32 to extraction column 12, in which the extraction of the free fatty acids takes place, whereby the extraction medium circuit is closed.
• the energy required for distillation in the form of heating steam is fed through lines 34 and 36 to the distillation columns 20 and 28.
• Example 1 250 g of an oil composed of 95.5% by weight of neutral oil, 4.2% by weight of free fatty acids and 1.7% by weight of tocopherol were mixed at 50 ° C. with 100 g of 2-dimethylaminoethanol and 70 g Water mixed by stirring. After the mixing process had been interrupted and the two liquid phases had been separated, samples were taken from both phases and analyzed.
• the extractant-rich phase, minus the extractant contained 53.7% by weight of neutral oil, 45.0% by weight of free fatty acids and 0.3% by weight of tocopherol.
• the oil-rich raffinate phase minus the extractant contained 98.2% by weight of neutral oil, 0.05% by weight of free fatty acids and 1.8% by weight of tocopherol.
• Example 3 200 g of an oil with 5.1% by weight of free fatty acids and 0.3
• tocopherol was mixed with an extractant composed of 100 g of water and 100 g of pyridine extractant at 60.degree. After the mixing process had been interrupted and the phases separated, a sample was taken from each of the two coexisting liquid phases and analyzed. The loading of the extractant was 2.1% by weight.
• the extract, minus the extractant consisted of 20.8% by weight of free fatty acids, 0.3% by weight of tocopherols and 95.8% by weight of glycerides.
• the raffinate minus the extractant contained 4.2% by weight of free fatty acids, 0.3% by weight of tocopherols and 95.1% by weight of glycerides.
• the raffinate contained 0.05% by weight of free fatty acids, 1.4% by weight of tocopherol, 0.6% by weight of stigmasterol and 97.95% by weight of neutral oil. 0.46% by weight of the amount of neutral oil used remained in the extract.
• the raffinate minus the extractant consisted of 0.3% by weight of free fatty acids, 0.4% by weight of tocopherols, 0.1% by weight of stigmasterol, and 99.4% by weight of neutral oil. 6% by weight of the amount of neutral oil used was in the extract. The solvent ratio had the low value of 0.14.
• Example 6 100 g of palm oil containing 5.5% by weight of free fatty acids were mixed at 60 ° C. with 100 g of a mixture of 30 g of N, N- Dimethylamino-ethanol and 70 g water mixed together by stirring. After the mixing process had been interrupted, the phase separation, which had taken place after about 3 minutes, was waited for and samples were taken from both coexisting phases and analyzed.
• the palm oil (raffinate) minus the extractant contained less than 0.1% by weight of free fatty acids.
• the extract contained less extractant 77% by weight of fatty acids and 23% by weight of glycerides (mono-, di- and triglycerides; the latter the main component). About 1.2 g glycerides (approx. 1.2% of the weight) were extracted together with the free fatty acids.
• the extract contained less extractant 67% by weight of fatty acids and 33% by weight of glycerides (mono-, di- and triglycerides).
• the raffinate less extractant contained less than 0.1% free fatty acids.
• the extract contained 2 g of glycerides (approx. 2% of the weight). 1.9% by weight of N, N-dimethylaminoethanol were dissolved in the raffinate and washed out with water.
• 0.19% secondary components (tocopherols + tocotrienols + phytosterols) are dissolved in 400 g heptane fraction at 40 ° C.
• the solution is extracted with 600 g of a solution of 40% N, N-dimethylaminoethanol in water at 40 ° C.
• the extract (the one dissolved in the extractant) contains less extractant 96% fatty acids.
• the raffinate minus the extractant consists of 13.4 g glycerides, 0.7 g free fatty acids, and 0.3 g secondary components (2% tocopherols + tocotrienols + phytosterols).
• DMAE dimethylaminoethanol
• the raffinate stream leaving the extraction column 12 comprised 24.424 kg / h neutral oil, 0.090 kg / h free fatty acids, 0.855 kg / h DMAE and 0.855 kg / h water.
• the extract stream consisted of 14.145 kg / h DMAE, 14.145 kg / h water, 0.285 kg / h neutral oil and 1.20 kg / h free fatty acids.
• the raffinate stream was fed to the washing column 16, in which it was countercurrented at 80 ° C. with 15.0 kg / h of water
• DMAE was washed out.
• the raffinate stream thus purified left the washing column 16 in the following composition: 28.424 kg / h neutral oil, 0.012 kg / h DMAE and less than 0.025 kg / h free fatty acids. This corresponds to a neutral oil with 0.00042% by weight DMAE and less than 0.00088% by weight free fatty acids.
• the wash water left the wash column 16 with the following composition: 15.855 kg / h of water, 0.855 kg / h of DMAE and 0.064 kg / h free fatty acids.
• the wash water was regenerated in the distillation column 20 at 100 ° C. As the top product, 15.0 kg / h of water were returned through line 24 to the washing column 16.
• the bottom product with 0.855 kg / h of water and 0.855 kg / h of DMAE is combined with the extract stream from the extraction column 12 flowing through the line 26.
• the extract stream from the extraction column 12 combined with the bottom product from the distillation column 20 was fed to the distillation column 28.
• the top product of the distillation column 28 from 15.0 kg / h of water and 15.0 kg / h of DMAE was recycled as the extractant through line 32 into the extraction column 12.
• the distillation column left 28 0.285 kg / h neutral oil and 1.264 kg / h free fatty acids. Accordingly, the extract consisted of 18.4% by weight of neutral oil and 81.6% by weight of free fatty acids.
• the extraction agent cycle is thus closed and there are no waste disposal problems.

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